We randomly assigned 4589 healthy nulliparous women who were 13 to 21 weeks pregnant to receive daily treatment with either 2 g of elemental calcium or placebo for the remainder of their pregnancies. Surveillance for preeclampsia was conducted by personnel unaware of treatment-group assignments, using standardized measurements of blood pressure and urinary protein excretion at uniformly scheduled prenatal visits, protocols for monitoring these measurements during the hospitalization for delivery, and reviews of medical records of unscheduled outpatient visits and all hospitalizations. Calcium supplementation did not significantly reduce the incidence or severity of preeclampsia or delay its onset. Preeclampsia occurred in 158 of the 2295 women in the calcium group (6.9 percent) and 168 of the 2294 women in the placebo group (7.3 percent) (relative risk, 0.94; 95 percent confidence interval, 0.76 to 1.16). There were no significant differences between the two groups in the prevalence of pregnancy-associated hypertension without preeclampsia (15.3 percent vs. 17.3 percent) or of all hypertensive disorders (22.2 percent vs. 24.6 percent). The mean systolic and diastolic blood pressures during pregnancy were similar in both groups. Calcium did not reduce the numbers of preterm deliveries, small-for-gestational age births, or fetal and neonatal deaths; nor did it increase urolithiasis during pregnancy. Additional analyses utilizing the study database are being performed. During FY00 a manuscript on outcomes in healthy nulliparas who subsequently developed hypertension and another on maternal calcium supplementation in relation to fetal bone mineralization were published in Obstetrics and Gynecology. Two manuscripts are in press at the American Journal of Obstetrics and Gynecology: one on nutrient intake and the hypertensive disorders of pregnancy and another on outcomes of pregnancies with a rise in diastolic blood pressure >15 mm Hg to a level <90 mm Hg with proteinuria. A manuscript on urinary isoprostanes in severe preeclampsia has been submitted for publication. Other studies are underway on the following topics: diet, ethnicity, and birthweight; urinary kallikrein as an early indicator of preeclampsia; and urinary insulin in preeclampsia, gestational hypertension, and gestational diabetes mellitus.